Aguero, 26, spent the 2010 season with the Pirates' High-A and Double-A affiliates, posting a 6.14 ERA, 7.7 K/9, 5.2 BB/9, and 0.3 HR/9 in 29 1/3 relief innings. He was designated for assignment by the Bucs in March to open a spot for Jose Veras, and later claimed off waivers by the Rangers. Prior to the season, Baseball America ranked Aguero 19th among Pirates prospects, noting that his fastball can reach the high 90s but there are concerns about his health and toughness.